Directional charge explosive device



NOV. 11, 1969 w p, c E Rm ET AL 3,477,372

DIRECTIONAL CHARGE EXPLOSIVE DEVICE Filed Dec. 11, 1967 INVENTORS pWILL/AM DON MCFRK/N BY HAKVE NELSON ATT IPA/5Y5 "United States Patent3,477,372 DIRECTIONAL CHARGE EXPLOSIVE DEVICE William D. McFerrin, 335Phillips Ave., Sparks, Nev. 89431, and Harve P. Nelson, 1235 PalisadesDrive, Reno, Nev. 89502 Filed Dec. 11, 1967, Ser. No. 689,405 Int. Cl.F4211 3/08, 1/02 US. Cl. 102-24 2 Claims ABSTRACT OF THE DISCLOSURE Adirectional charge explosive device is provided with a dome-shapedcasing and a bottom cover which entirely encloses the bottom of thecasing and has therein a central downwardly opening circular concavityand an outer downwardly opening semi-toroidal concavity. The concavitiesin the bottom cover, when used in conjunction with a 360 over-drivedetonation arrangement, direct the force of the detonated explosivecharge in the desired direction.

BACKGROUND OF THE INVENTION Field of the invention A directional chargeexplosive device unit is provided with a central concavity and an outerconcavity, and a 360 over-drive detonation arrangement, all three beingsubstantially concentric with the central vertical axis of the device.

Description of the prior art The closest prior art known to applicantsis Woiiord et al. 3,244,102. This patent is discussed and distinguishedhereinafter.

SUMMARY OF THE INVENTION A directional charge explosive device is usedto reduce large rocks, boulders, pieces of concrete and the like intofragments which can be more easily handled, positioned and removed. Manytimes a secondary blasting unit, such as the directional chargeexplosive device of this invention, only comes into usage after aninitial larger detonation has blasted material from a hillside or thelike.

Typical of the heretofore used secondary blasting units is a patentissued to Wotford et al., 3,244,102. The device in 3,244,102 issatisfactory for most blasting operations but the device of the presentinvention has improved the directional accuracy and is of improvedmechanical construction. Applicants have improved the above describeddevice by providing an improved secondary blasting unit having formedtherein a central downwardly opening circular concavity as well as anouter downwardly opening semi-toroidal concavity used in conjunctionwith a 360 over-drive detonation arrangement.

It is the primary object of the present invention to provide a new andimproved directional charge explosive device.

Another object of the invention is to provide a directional chargeexplosive device with a double seal between the casing and the bottomcover.

A further object of the present invention is to provide a plurality ofdownwardly opening concavities in the bottom cover to insure increaseddirectional effect of the detonation.

A further object of the present invention is to provide a 360 over-drivedetonation arrangement which is substantially concentric with thecentral vertical axis of the device.

A further object is to provide a directional charge explosive devicewhich produces a great breaking power with the use of a small amount ofexplosive.

Patented Nov. 11, 1969 BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is anisometric or perspective view illustrating the secondary blasting unitof the present invention.

FIGURE 2 is a top plan view.

FIGURE 3 is an enlarged sectional view taken substantially as indicatedalong line 33 of FIGURE 2.

FIGURE 4 is a fragmentary view taken substantially as indicated alongline 4-4 of FIGURE 3 and illustrating the detonating cap cavity and theinterior opening recesses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, thedirectional charge explosive device of the present invention, generallyindicated 10, which is intended for use in any type of secondaryblasting application, is provided with a domed-shaped casing 12 and abottom cover 14. The domed-shaped casing 12 is substantially concentricwith a central vertical axis indicated by line 16 and terminates in asubstantially circular lower rim 18 having a groove 20 on the lower sidethereof. The casing 12 has a planar upper central portion 22 surroundedby curved walls 24.

The bottom cover 14 has formed therein a central downwardly openingcircular concavity 26 and an outer downwardly opening semi-toroidalconcavity 28 in order to focus the heat and energy of the explosivesinto a very small area. Both of the concavities 26 and 28 aresubstantially concentric with the central vertical axis 16. The focalpoint of convergence of concavity 26 is below the bottom cover 14 andthe focal point of convergence of concavity 28 can be on the bottomcover 14 or below it as desired, thus making concavity 26 less than onehalf a sphere and concavity 28 at most one half a sphere. Casing 12 andcover 14 enclose a central chamber 30 and by means of lip portion 32 ofthe bottom cover 14, which overlaps the circular lower rim 18 of thecasing 12, and rib 34, which matingly fits into the groove 20, provide adouble seal between the casing 12 and the cover 14 so that thedirectional charge explosive device of the present invention can be usedunder all weather, temperature, surface and marine conditions. Aplurality of pointed members 36 may be provided on the bottom cover ifdesired to insure positional stability of the directional chargeexplosive device. A material such as plastic which can be readily moldedinto the desired shape has been found suitable for making the casing 12and cover 14.

Located within the central chamber 30 is a charge of explosive filler 38which is of the alkali nitrate category and detonates at aself-propagating rate of approximately 14,000 to 15,000 feet per second.The explosive filler 38 is of a regular commercial type and it is wellknown to the art. The relative weight strength or explosive equivalentof this explosive filler 38 is normally However in certain applicationsof this directional charge explosive device it has been found that theexplosive filler 38 should have a lower relative weight strength orexplosive equivalent. A detonating fuse 40 is positioned in an annularchannel 42 in the casing 12 with the ends of the fuse 40 beingcoterminous in a lower recess 44. Plug 46 is provided to protect thefuse 40. The detonating fuse 40 is commercially made and detonates atthe rate of approximately 20,000 to 22,000 feet per second. As can beseen in FIGURE 3, the diameter of the annular channel 42 as measuredfrom the vertical axis 16 is approximately equal to the mean diameter ofthe semitoroidal concavity 28.

The various strengths of the explosive filler 38 that may be used in thedirectional charge explosive device are cap-sensitive explosives and donot require dynamite as a booster. The explosive fillers when properlyinitiated, have considerably more power than the standard dynamites. Toget the maximum efiiciency, it is essential that the peak velocity ofthe explosive fillers be reached as quickly as possible. This isaccomplished by using the proper initiation device for the particularexplosive.

As can be seen in FIGURE 2, the annular channel 42 allows the fuse 40 tohave a 360 shape. This generates a force wave which travels at severaltimes the speed of sound within the 360 loop when the fuse 40 isdetonated. This creates a tremendous shock to the localized area therebycreating an efficient over-drive detonation mechanism for the explosivefiller.

The term over-drive, as used in the industry, describes that property ofexplosives which enables them to detonate at a rate greater than theirself-propagating detonation rate. For example, an explosive whichdetonates at the rate of 22,000 feet per second (detonating fuse) is setoff in contact with another explosive which detonates at the rate of15,000 feet per second (explosive filler) then this 15,000 feet persecond explosive will detonate at a rate higher than 15,000 feet persecond but somewhat lower than 22,000 feet per second.

Therefore, by using this principle the detonation velocity of theexplosive filler can be increased from approximately 15,000 feet persecond to over 18,000 feet per second as desired. In addition, thismethod of detona tion of the explosive filler greatly improves theresults of the new directional charge explosive device of the presentinvention.

Radial boss 48 on the upper portion of the casing 12 houses the lowerrecess 44 and the upper exterior opening cavity so with frangible walls52 separating the recess 46 and the cavity 50. The cavity 50 is providedwith slit 54 in order to allow spreading or flaring when detonating caps56 of various sizes are inserted into it. Handle 58 is provided for easein handling.

In actual operation and after the directional charge explosive device isproperly positioned on or near the target object, the detonating cap 56is ignited. The force of the detonating cap 56 ruptures the frangiblewalls 52 and in turn detonates the ends of the detonating fuse 40. Thedetonating fuse 40 then causes detonation of the explosive filler 38 totake place along the path of the annular channel 42, thus providing aninstantaneous accelerated detonation of the filler 38 which results in avortiginous propagation front which in turn accentuates the toroidalblast of the device 10.

Due to the focal point of the convergence of the plural concavities, theenergy of the explosion is transmitted within the target object causingthe target object to fail from implosion resulting from the explosion ofthe directional charge explosive device positioned on the periphery ofthe target object. Since an implosion is created, there is no dangerthat men and/or machinery will be damaged by flying rocks and debris. Inaddition, there is a tremendous saving in the cost of labor, time andequipment in that no drilling operation precedes the utilization of thedirectional charge explosive device of this invention.

In numerous actual field tests, the device of this invention has beenable to average over one cubic yard of breakage per pound of explosivefiller.

We claim:

1. A directional charge explosive device comprising:

(a) a dome-shaped casing substantially concentric with a centralvertical axis, said casing terminating in a substantially circular lowerrim,

(b) a planar bottom cover mounted on said lower rim and entirelyenclosing the bottom of said casing, said casing having formed therein acentral downwardly opening circular concavity having its focal point ofconvergence below the plane of the bottom cover and an outer downwardlyopening semi-toroidal concavity having its focal point substantially inthe plane of the bottom cover, both of said concavities beingsubstantially concentric with said central vertical axis and theperipheral edges of both concavities being in substantially the plane ofthe bottom cover;

(c) a radial boss on the upper portion of said casing, said boss beingformed with an exterior opening cavity to receive a detonating cap, andan interior opening recess alongside said cavity and separate therefromby frangible walls;

(d) an explosive charge in said casing; and a circular detonating fusein said casing and extending substantially 360 in contact with saidcharge, said circular fuse being substantially concentric with saidcentral vertical axis, the ends of said detonating fuse terminating insaid recess.

2. The directional charge explosive device of claim 1 wherein theexterior opening cavity has a slit whereby the cavity can be spread sothat detonating caps of various sizes may be inserted therein.

References Cited UNITED STATES PATENTS 2,856,850 10/1958 Church at al.

2,934,014 4/1960 Smith et a1. 10228 X 3,244,102 4/ 1966 Wofford et a1.

3,347,164 10/1967 Baks et al.

VERLIN R. PENDEGRASS, Primary Examiner

